Generally, in the treatment of spine related diseases, indirect treatment methods through physical therapy and direct treatment methods that adjust and fix the spine by mounting a separate fixing device into a damaged part of the spine are performed. That is, in the case of mild spinal diseases, physical therapy is performed, but in the case of severe diseases in the cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacrum and intervertebral disk that make up the spine, treatments are conducted using a separate spine fixing device.
Commonly used spine fixing devices include a pedicle (sacral) screw that is inserted into the pedicle or sacrum of the vertebra at a predefined angle and depth, a spinal rod that is disposed on one side of the part of the spine, and a fixing cap or a coupling fastener that fastens the spinal rod and the pedicle screw together, in order to adjust the damaged part of the spine to the normal condition and fix it without movement. To treat the damaged part of the spine, the pedicle screw is first inserted into and fixed onto the pedicle or the sacrum of vertebra in an appropriate orientation and position, then the part of the spine is adjusted to normal condition using the spinal rod, and lastly, the spinal rod and the fixing screw are secured using the fixing cap or coupling fastener, completing the treatment.
Meanwhile, recently, with the aging population, screw fixation is increasingly used for patients with severe osteoporosis. However in the case of conventional screw fixation (Korean Patent Application No. 10-2006-0133857), after the screw fixation is performed, the bones around the screw fixed to the bone may resolve over time, otherwise known as halo, a bone cavitation phenomenon which causes a screw loosening phenomenon. Consequently, nearly half of the patients who undergo the screw insertion may experience adjacent segment degeneration as a screw fixation aftermath, requiring reoperation which becomes a physical and economic burden to the patients.
In this case, a larger screw may be inserted into the position at which the screw loosening phenomenon occurred, or the bones around the screw may be filled with cement or transplanted with allograft bone plug. However, it was previously difficult to obtain secure fixation of the screw into the bone through this method.